The present invention relates to a joint having a ball and a shaft which are coupled to each other through plastic deformation and more particularly to a joint having a ball and a shaft suitable for a ball joint used in an internal combustion engine or a piston mechanism.
In, for example, Japanese Patent Publication 96377/86 a piston mechanism has been widely used in, for example, an automotive compressor includes a piston portion reciprocating within a cylinder and a piston rod for mechanically connecting the piston portion and a swash drive plate to each other.
In such a structure, almost all of piston rods are of the spherical head couple type and are made of steel since the piston rods are used mainly for reciprocating motion. Such spherical head couple type piston rods have been usually cast as one-piece elements or the ball and shaft portions have been made separately and bonded to each other through a weld technique; however, no processes other than casting and postbonding have been proposed. However, cast piston rods must be ground in a post process, thereby reducing production efficiency and economy. Also, in bonding the ball portions and the shaft portion, it is very difficult to obtain a satisfactory mechanical accuracy, which would lead to an increase in cost.
In a method of separately forming the ball and the shaft portions and bonding them by welding, although it is easy to form the respective ball and shaft portions, it is very difficult to obtain a satisfactory mechanical accuracy as in the former case and, consequently, this method is not suitable for mass-production. Moreover, even if the shaft is made of light metal such as aluminum for reducing its weight, present welding techniques cannot offer a reliable bond between the aluminum material and iron material and, consequently, are not practical use.
The avoid the above-noted disadvantages, an object of the present invention resides in providing a joint having a ball and a shaft, which is superior in mass-production with a high mechanical accuracy.
The present invention provides a joint in which a shaft is inserted into a mounting hole formed in a ball so that either of the shaft and a fitting peripheral portion of the ball is locally plastically deformed, thus bonding the shaft to the mounting hole with a tightening force.
With a structure wherein the shaft and the ball receiving the shaft are bonded to each other by local plastic deformation, it is possible to manufacture the joint with a simple pressing process. Therefore, it is possible to provide the joint, having the ball and shaft, that has a high accuracy and is capable of mass-production.